The present invention relates to a package for dry-resist material which is wound up into rolls or stacked in the form of sheets.
So-called "dry resists" include photoresists which can be processed with aqueous-alkaline solutions or organic solvents and are formed of three-layer systems, in which the photopolymer layer is sandwiched between a support film and a protective film. The support film used frequently includes a polyester film, for example, of polyethylene terephthalate, and the protective film can be a polyolefin film, for example, of polyethylene.
For sale, transportation and storage, the photoresists are, in general, wound up into rolls, wrapped in opaque packaging films and placed in cardboard boxes. The material used for the packaging films often includes polyethylene which has been dyed with carbon black. To the end faces of the winding cores of the rolls, square or rectangular discs are attached, which are to protect the rolls from mechanical damage during transport and handling.
The known package serves, in the first place, to protect the photoresists from an undesirable influence of light, in particular, ultraviolet radiation, from atmospheric effects, from mechanical damage during transport, and from soiling.
In practice, it appears that, after transport over relatively long distances and/or prolonged storage periods, photoresists packaged in this way tend to form fused places at the front edges, which are particularly pronounced at the front edges close to the winding core of the roll. In these cases, small amounts of the photoresist emerge from the front edges of the roll and cause the individual layers of the roll to stick together. Fused places of this kind drastically hamper processing of the dry resist, since upon unwinding the photoresist from the roll, small resist particles are torn away which may soil the plates, for example, printing plates or printed circuit boards, to which the photoresist is laminated. Such fused places at the front edges of photoresist rolls do not only occur as a result of long storage periods. Instead it has been found that the storage conditions as such also have a considerable influence on the processing characteristics of a photoresist. It can happen, for example, that a photoresist roll which has been stored for one year can still be processed without difficulty, while another photoresist roll, from the same batch, which has been stored in another place under different storage conditions has become useless for processing after only three months.
This different behavior of photoresist material coming from the same batch clearly shows that the storage conditions and the mode of transport have a considerable influence on the processability of the photoresist material. Closer investigations show that the fused places at the front edges of the photoresist rolls can be attributed to the flow of the photopolymer layer of the photoresist material.